The present invention broadly relates to a new and improved construction of an apparatus for regulating the warp section tension during warping.
In its more particular aspects, the present invention concerns an apparatus for regulating the warp section tension during warping, wherein warp threads are removed from the bobbins of a warp creel. Each of the warp threads are passed by means of a respective associated adjustable and settable thread brake to a reed arranged on the warping carriage of the warping machine and are there ordered or arranged in the form of a warp section prior to winding onto the warping drum. There is also provided a central brake adjustment device which is coupled with a tension measuring device and serves to automatically control the thread brakes during the operation of the warping machine.
Such an apparatus is known, for example, from German Patent Publication No. 2,853,662 published July 3, 1980. This known apparatus measures in each case the tension of a single thread, if desired for each side of the warp creel and the central adjustment of all of the thread brakes of the warp creel or the relevant warp creel side takes place on the basis of this single thread measurement. However, the tension of this single measured thread cannot be representative of the tension of all of the remaining, non-measured threads of a warp section, because, namely, the measured thread undergoes an additional deflection for performing the measurement operation and which does not occur in the case of the non-measured threads and also because the different tension conditions are ignored. These different tension conditions can be due to possible use of different threads or yarns or the like within a warp section or different bobbin diameters, as well as different positions of the bobbins in the warp creel.
Additionally, in this known apparatus the tension measuring device is located in the vicinity of the warp creel, so that no account is taken of any following locations or points in the thread travel or movement direction which also influence both the measured thread and the remaining threads, particularly those in the vicinity of the warping carriage, for example, the lease reed, the warp reed and possibly used further deflection rollers during regulation.
This leads to incorrect or at least imprecise tension measurement results. Thus, with the known apparatus, it is scarcely possible to control the central brake adjusting device such that the uniform thread tension of all the threads necessary for obtaining a completely satisfactory warp or warp sheet during warping is achieved. Moreover, in the known apparatus, thread tension regulation cannot take place at the time of starting or run-up of the warping machine.
In a different context, namely, beam warping machines, it is admittedly known, for example, from German Patent Publication No. 2,724,334, published Dec. 7, 1978 and Swiss Pat. No. 558,293 granted Dec. 15, 1974 to use a group of threads or thread field or parts thereof for measuring the winding tension. In the apparatus according to the aforementioned German Pat. No. 2,724,334, it is a question of measuring the tension of the threads running over a tension measuring roller independently of the varying wrap angle due to the increased application of the threads to the back beam. In the aforementioned Swiss Pat. No. 558,293, part of the material web width, for example, the threads from a creel stage are led over a measuring and control roll at the creel outlet and the measured values thereof are then used for controlling the winding speed.